The production of ethyl (diethoxymethyl) phosphinate has been described in Gallagher, M. J. Honegger, H. Aust. J. Chem. 1980, 33, 287-294 (see below). The phosphinic acid was obtained by evaporation of commercial aqueous solutions (50 wt % water).
EP 307362 A2 describes the production of aliphatylphosphinic acid derivatives from aqueous phosphinic acid.
A process for esterification of hypophosphite salts has been published in Deprèle, S. Montchamp, J.-L. J. Organomet. Chem. 2002, 643-644. 154-165 and is outlined below:

One object of the present invention was to develop a process for the production of alkyl dialkoxyalkylphosphinates that is more suitable for large-scale production.
Outline of the Invention
The present invention is directed to a new process for the production of alkyl dialkoxyalkylphosphinates of formula (I):
wherein    R1, R2 and R3 each and independently represents methyl or ethyl; and    R4 represents hydrogen or methyl;    whereby a hypophosphite salt is reacted with a compound of formula (II):
wherein    R1, R2, R3 and R4 are as defined above;    in the presence of a solvent and an acid.
The process according to the present invention may be used for the synthesis of inter alia ethyl (diethoxymethyl) phosphinate. By using this method the hazardous handling of neat phosphinic acid can be avoided. Further, the amount of by-products may be controlled.
Methods of Preparation
In one embodiment of the invention, the compound of formula (II) is charged to a stirred slurry of hypophosphite salt and a suitable solvent such as toluene-ethanol (20:1). The mixture is carefully inerted and acid is charged at a controlled speed. The slurry is stirred at from 0° C. to 20° C. during 1 to 20 hours or until most of the intermediate alkyl ester is consumed. The mixture is quenched by the addition of aqueous sodium hydrogen carbonate and the organic layer is concentrated.
In one embodiment of the present invention, the hypophosphite salt is selected from ammonium hypophosphite, sodium hypophosphite and potassium hypophosphite.
In one embodiment of the present invention, the compound of formula (II) is selected from trimethylorthoformate, triethylorthoformate, trimethylorthoacetate and triethylorthoacetate.
In one embodiment of the present invention, the acid used in the reaction is selected from methane sulphonic acid, sulphuric acid, boron trifluoride etherate and trifluoromethane sulphonic acid. In a further embodiment of the invention, the acid is essentially water-free. In one embodiment, the acid contains up to 10% water, up to 5% water or up to 2% water.
In one embodiment, the solvent used in the process according to the present invention is toluene, acetonitrile, tetrahydrofuran (THF), methylene chloride, benzene or a mixture of toluene and ethanol.